It is generally known to use an electrical device to evaporate a perfume and/or fragrance composition into a space, particularly a domestic space, such as a living room, to provide a pleasant aroma. There are a variety of such devices on sale, for example, AIRWICK® Diffuser ACTIF® (manufactured by Reckitt Benckiser), RENUZIT® Triscents (manufactured by Dial Corp.), or AMBI-PUR® fragrance diffuser (manufactured by Sara Lee). Generally, these devices consist of a perfume or fragrance source, an electrical heater, a capillary element or substrate from which the perfume is vaporized by application of heat, and a power supply. This arrangement provides a continuous supply of the perfume to the space in which the device is placed. However, it may take longer to fragrance a room, because this arrangement relies on vaporization involving the generation of smaller molecules that diffuse quickly and are more easily absorbed into surrounding objects.
One effort to address these problems is described in U.S. Pat. No. 6,752,327, Martens et al. The Martens patent discloses a plug-in air freshener having a piezoelectric actuator that vibrates a tilted orifice plate to dispense perfumes. The device disclosed in the Marten patent includes a wick and a piezoelectric actuator which is physically coupled to an orifice plate. However, the coupled piezoelectric actuator may cause bimodal droplets of perfume which may still deposit on the adjacent wall surface even with the titled orifice plate and the upwardly extending protrusion positioned between the orifice plate and the adjacent wall surface. Bimodal droplets are droplets that have already passed through an emitting orifice and fall back onto the emitting orifice to be emitted into the atmosphere a second time, but this time without passing through the emitting orifice. A vibrating perforate plate coupled to a piezoelectric actuator can provide such bimodal droplets. Bimodal droplets that undergo such process are generally larger partly because they are not limited by the size of the perforations in the emitting orifice. In addition to surface deposition, the tilted, coupled piezoelectric actuator device disclosed in Martens does not appear to address the problem that some liquid perfumes fall back onto the plate and flow forward, leaking down openings of the housing or off of the device and onto the floor or surrounding surfaces. Furthermore, when the device in Martens is not activated, a background level of perfume continues to be evaporated into the atmosphere. This effect causes the well-known phenomenon of scent habituation or olfactory fatigue.
The device described in WO 2007/062698A1, Hess et al., attempts to solve the deposition problem by utilizing a decoupled piezoelectric system. The Hess reference discloses a volatile liquid droplet dispenser device having a decoupled piezoelectric actuator positioned eccentric to the wick. However, the device described in Hess may still cause some deposition on surrounding surfaces. Therefore, there remains a continuing need for an improved device for fragrancing larger areas, while reducing surface deposition and improving noticeability of a fragrance over time.